Rotational position determination apparatus

ABSTRACT

A rotational position determination apparatus is configured to determine an entry rotational position, which defines a rotational position of an insertion device like a stent at an entry site, such that a navigation of the insertion device from the entry site to a target site along an inner path results in a rotational position of the insertion device at the target site being equal to a desired target rotational position based on a representation of the inner path and the desired target rotational position. If the insertion device is arranged in the determined entry rotational position at the entry site and then navigated to the target site, it is therefore not necessary to rotate the insertion device at the target site.

CROSS-REFERENCE TO PRIOR APPLICATIONS

This application a divisional application of U.S. patent applicationSer. No. 14/117,389, filed Nov. 13, 2013, which is the U.S. NationalPhase application under 35 U.S.C. § 371 of International ApplicationSerial No. PCT/IB2012/052679, filed on May 29, 2012, which claims thebenefit of European Patent Application Serial No. EP11168893.3, filed onJun. 7, 2011. These applications are hereby incorporated by referenceherein

FIELD OF THE INVENTION

The invention relates to a rotational position determination apparatus,a rotational position determination method and a rotational positiondetermination computer program for determining a rotational position ofan insertion device for being inserted into an object at an entry siteand for being navigated along an inner path within the object to atarget site within the object. The invention relates further to arotational positioning assistance apparatus and a rotational positioningassistance method for assisting in positioning the insertion device, anda rotational positioning apparatus and a rotational positioning methodfor positioning the insertion device.

BACKGROUND OF THE INVENTION

US 2009/0304245 A1 discloses a method for a structurally individualizedsimulation of a wall support element introduced into a section of atubular structure. Image data of the interior of the section of thetubular structure are provided and a start point and an end point of thesection of the tubular structure are determined, wherein between thestart point and the end point a lumen and a profile line of the tubularstructure are determined. Furthermore, an individual elastic structuremodel for the section of the tubular structure is identified by adaptinga tubular elastic initial model to the section of the tubular structureon the basis of the identified lumen and the profile line, and a tubularelastic wall support element model which is positioned inside theindividual structure model is provided. The wall support element modelis then virtually and stepwisely expanded, wherein in each expansionstep a check for collisions between the wall support element model andthe individual structure model is carried out. At the positions where acollision is identified, the wall support element model and theindividual structure model are modified at least locally while takinginto account the elasticity of the individual structure model.

US 2010/0036390 A1 discloses a method for delivering a stent to abifurcation of a vessel. A first guidewire is advanced through a bodylumen to a first branch of a vessel bifurcation. A second guidewire isadvanced through a body lumen to a second branch of the vesselbifurcation. Moreover, a catheter assembly is advanced to the vesselbifurcation along the first guidewire and the second guidewire, whereinthe catheter assembly comprises a catheter shaft defining a firstguidewire lumen for receiving the first guidewire and a balloonrotatably disposed about the catheter shaft, wherein the balloon isfreely rotatable about the first guidewire. The catheter assemblyfurther comprises a tubular member engaged to an external surface of theballoon, wherein the tubular member defines a second guidewire lumen forreceiving the second guidewire, and a stent, wherein the stent isdisposed about at least a portion of the balloon and the tubular memberand wherein the second guidewire passes through at least one openingdefined by the stent. The balloon is rotatable about the firstguidewire, in order to allow the stent to be arranged in a desiredrotational position. For providing this rotation functionality atechnically relatively complex construction of the catheter assembly isrequired.

SUMMARY OF THE INVENTION

It is regarded as being an object of the present invention to provide arotational position determination apparatus, a rotational positiondetermination method and a rotational position determination computerprogram for determining a rotational position of an insertion device forbeing inserted into an object at an entry site and for being navigatedalong an inner path within the object to a target site within theobject, wherein the determination of the rotational position allows touse a technically less complex interventional device for inserting theinsertion device. It is a further object of the present invention toprovide a rotational positioning assistance apparatus and a rotationalpositioning assistant method for assisting in positioning the insertiondevice, and a rotational positioning apparatus and a rotationalpositioning method for positioning the insertion device, which allowusing a technically less complex interventional device for inserting theinsertion device.

In a first aspect of the present invention a rotational positiondetermination apparatus for determining a rotational position of aninsertion device for being inserted into an object and for beingnavigated along an inner path within the object from an entry site to atarget site within the object is presented, wherein the rotationalposition determination apparatus comprises:

-   -   an inner path providing unit for providing a representation of        the inner path within the object,    -   a target rotational position providing unit for providing a        desired target rotational position of the insertion device at        the target site,    -   an entry rotational position determination unit for determining        an entry rotational position, which defines a rotational        position of the insertion device at the entry site, such that a        navigation of the insertion device from the entry site to the        target site along the inner path results in a rotational        position of the insertion device at the target site being equal        to the desired target rotational position based on the        representation of the inner path and the desired target        rotational position.

Since the entry rotational position determination unit determines theentry rotational position such that a navigation of the insertion devicefrom the entry site to the target site along the inner path results in arotational position of the insertion device at the target site beingequal to the desired target rotational position based on therepresentation of the inner path and the desired target rotationalposition, the insertion device can be arranged at the entry site in thedetermined entry rotational position such that, after the insertiondevice has been moved from the entry site to the target site along theinner path, the insertion device is correctly located at the target sitein the desired target rotational position. It is therefore not necessaryto rotate the insertion device at the target site, i.e. it is notnecessary to provide a technically complex interventional device forinserting the insertion device.

In an embodiment, the inner path providing unit is a storing unit, inwhich the representation of the inner path within the object is stored,wherein the stored inner path can be provided by the storing unit forsimulating the navigation of the insertion device from the entry site tothe target site. Also the target rotational position providing unit canbe a storage unit, in which the desired target rotational position ofthe insertion device at the target site is stored, wherein the storeddesired target rotational position can be retrieved from the storageunit for providing the desired target rotational position.

The object is preferentially a person or an animal, wherein the targetsite is preferentially located within a vessel like the aorta artery oran organ like the heart.

The insertion device is preferentially a device which is insertable intothe object. In particular, the insertion device is an implantable devicelike a stent. In an embodiment, the insertion device is an endovasculardevice. For example, the endovascular device is an asymmetricendovascular device like a fenestrated stent, which may be two-legged orwhich may comprise more legs, or a multi-branched stent. The rotationalposition determination apparatus allows therefore correctly positioningan endovascular device, without providing the endovascular device or adelivery unit comprising the insertion device for delivering the samewith a mechanism for rotating the endovascular device within a person oran animal, in particular, within an organ or a vessel of the person orthe animal.

It is preferred that the entry rotational position determination unit isadapted to simulate the navigation of the insertion device from theentry site to the target site based on the representation of the innerpath and the desired target rotational position for determining theentry rotational position. However, the entry rotational positiondetermination unit can also be adapted to determine the entry rotationalposition without performing a simulation. For example, if, in anembodiment, the inner path is relatively straight and has a relativelylarge diameter such that a rotation of the insertion device is notrequired while being navigated from the entry site to the target site,the entry rotational position can be determined as being equal to thedesired target rotational position, or, if it is known from, forinstance, a data base, that a navigation along the actual inner pathrequires a rotation of the insertion device by a certain known angle,the entry rotational position can be determined based on the providedtarget rotational position and the certain known angle, withoutnecessarily performing a simulation.

The insertion device can be navigated along the inner path by using adelivery system, wherein the entry rotational position determinationunit is adapted to determine the entry rotational position such that thenavigation of the insertion device from the entry site to the targetsite along the representation of the inner path by using the deliverysystem results in a rotational position of the insertion device at thetarget site being equal to the desired target rotational position basedon the representation of the inner path, the desired target rotationalposition and the delivery system. The delivery system preferentiallycomprises a delivery unit and a guidewire, wherein the delivery unitcomprises an insertion device, for example, a stent, and is movablealong the guidewire for transferring the insertion device from the entrysite to the target site. If the insertion device is held by the deliveryunit in a fixed spatial relationship, the entry rotational position ofthe insertion device can be determined by determining an entryrotational position of the delivery unit. If the entry rotationalposition is determined by simulation, the simulation can consider thefunctionality and dimensions of the delivery unit for determining theentry rotational position. The delivery unit is, for example, a knowndelivery unit for delivering the insertion device along the guidewire.

It is further preferred that the rotational position determinationapparatus comprises a three-dimensional vessel geometry model providingunit for providing a three-dimensional vessel geometry modelrepresenting a vascular network of the object, wherein the inner pathproviding unit is adapted to determine the inner path by determining apath through the three-dimensional vessel geometry model from the entrysite to the target site. The three-dimensional vessel geometry modelproviding unit is preferentially adapted to generate a three-dimensionalimage of a vascular network of the object and to segment thethree-dimensional image for extracting a three-dimensional vesselgeometry model. This allows automatically determining the inner pathaccurately such that the entry rotational position can reliably bedetermined.

In a preferred embodiment, the rotational position determinationapparatus further comprises a three-dimensional vessel geometry modelproviding unit representing a vessel configuration at least at thetarget site, wherein the insertion device is an endovascular devicebeing adapted to fit to the vessel configuration at the target site inat least one rotational position, wherein the target rotational positionproviding unit is adapted to determine the desired target rotationalposition such that the endovascular device fits to the vesselconfiguration at the target site. For example, if the endovasculardevice is a fenestrated stent, the target rotational position providingunit can be adapted to determine the desired target rotational positionof the fenestrated stent such that the apertures of the stent arecorrectly aligned with, for example, corresponding aortic side branches.

The rotational position determination apparatus preferentially furthercomprises an inner path element selection unit for selecting an innerpath element for being transferred along the inner path based oncharacteristics of the inner path determined from the representation ofthe inner path. This allows selecting an inner path element, which issuitable for being used along the respective inner path. In particular,the inner path element selection unit can be adapted to select adelivery system for delivering the insertion device to the target siteas the inner path element. For example, the length of the inner path canbe provided by an inner path length determination unit for determiningthe length of the inner path based on the provided representation of theinner path, wherein the inner path element selection unit can be adaptedto select guidewires having a length being optimized for the length ofthe respective inner path. In an embodiment, the inner path elementselection unit can comprise a data base, in which assignments betweeninner path elements and characteristics of the inner path like thelength, the maximal diameter, the minimal diameter, the minimalcurvature the maximal curvature, et cetera are stored, wherein asuitable inner path element can be selected from the data base based onthe assignments. For example, the flexibility of the guidewire can beselected based on the maximal curvature of the inner path.

The rotational position determination apparatus can further comprise anentry path providing unit for providing a representation of an entrypath from the outside of the object to an end of the inner path at theentry site, wherein the entry rotational position determination unit isadapted to determine the entry rotational position such that thenavigation of the insertion device from the entry site to the targetsite along the entry path and the inner path results in a rotationalposition of the insertion device at the target site being equal to thedesired target rotational position based on the representation of theentry path, the representation of the inner path and the desired targetrotational position. For example, the navigation of the insertion devicealong the entry path and along the inner path can be simulated based onthe representation of the inner path and the representation of the entrypath, in order to determine the entry rotational position at the entrysite at the outside of the object such that a navigation of theinsertion device from the outside of the object at the entry site alongthe entry path and along the inner path to the target site results in arotational position of the insertion device at the target site beingequal to the desired target rotational position. However, also regardingthe entry path the change of the rotational position obtained whilenavigating the insertion device along the entry path can be determinedwithout performing a simulation. For example, if, in an embodiment, theentry path is relatively straight and has a relatively large diametersuch that a rotation of the insertion device is not required while beingnavigated along the entry path, the change of the rotational position ofthe insertion device, which is obtained while navigating the insertiondevice along the entry path, can be zero, or, if it is known from, forinstance, a data base, that a navigation along the actual entry pathrequires a rotation of the insertion device by a certain known angle,the change of the rotational position obtained while navigating theinsertion device along the entry path can be determined by using thedata base.

The entry path providing unit can be adapted to provide the entry pathbased on an image of the entry site showing the entry path. For example,the entry path can be provided by an introducer sheath, which has beenintroduced at the entry site in a person to provide an access to anartery, in particular, an access to the femoral artery. The providedimage shows preferentially the introducer sheath and, thus, the entrypath. The provided image is, for example, a fluoroscopy image, whereinthe introducer sheath preferentially comprises markers visible in thefluoroscopy image such that the entry path is visible in the fluoroscopyimage. The entry path providing unit can be adapted to detect theintroducer sheath in the fluoroscopy image and to determine the entrypath depending on the detected introducer sheath.

In a further aspect of the present invention a rotational positioningassistance apparatus for assisting in positioning an insertion devicefor being inserted into an object at an entry site and for beingnavigated along an inner path within the inner object to a target sitewithin the object is presented, wherein the rotational positioningassistance apparatus comprises an indication unit for indicating adesired entry rotational position at the entry site determined by therotational position determination apparatus.

The rotational positioning assistance apparatus can indicate the correctentry rotational position to a user like a physician, in order to allowthe user to correctly arrange the insertion device at the entry site. Ifthe entry rotational position has been determined at the outside of anobject, in particular, at the outside of a person, at the entry site byconsidering the representation of the inner path and the representationof the entry path, the indication unit is adapted to indicate thedesired entry rotational position at the outside of the object at theentry site, for example, at the entrance of the entry path.

It is preferred that the indication unit is a display showing thedesired entry rotational position.

The rotational positioning assistance apparatus further comprises anactual entry rotational position determination unit for determining anactual entry rotational position of the insertion device at the entrysite, and a deviation calculation unit for calculating a deviationbetween the actual entry rotational position and the desired entryrotational position, wherein the indication unit is adapted to indicatethe desired entry rotational position by indicating the deviation. Theindication unit is, for example, a display, which can show a text or agraphic for advising the user to rotate the insertion device by an anglerepresenting the calculated deviation.

In a further aspect of the present invention a rotational positioningapparatus for positioning an insertion device for being inserted into anobject at an entry site and for being navigated along an inner pathwithin the inner object to a target site within the object is presented,wherein the rotational positioning apparatus comprises a positioningunit for positioning the insertion device at the entry site in an entryrotational position determined by the rotational position determinationapparatus. The rotational positioning apparatus can be used forautomatically positioning the insertion device at the entry site in thedetermined entry rotational position.

The positioning unit is preferentially adapted to rotate the insertiondevice to the entry rotational position. The rotational positiondetermination apparatus is preferentially adapted to determine the entryrotational position with respect to a reference rotational position. Thereference rotational position is preferentially also known by therotational positioning assistance apparatus and/or the rotationalpositioning apparatus, in order to allow the rotational positioningassistance apparatus and/or the rotational positioning apparatus toindicate the determined entry rotational position and/or to position theinsertion device at the entry site in the entry rotational position withrespect to the reference rotational position.

In a further aspect of the present invention a rotational positiondetermination method for determining a rotational position of aninsertion device for being inserted into an object at an entry site andfor being navigated along an inner path within the object to a targetsite within the object is presented, wherein the rotational positiondetermination method comprises:

-   -   providing a representation of the inner path within the object        by an inner path providing unit,    -   providing a desired target rotational position of the insertion        device at the target site by a target rotational position        providing unit,    -   determining an entry rotational position, which defines a        rotational position of the insertion device at the entry site,        such that a navigation of the insertion device from the entry        site to the target site along the inner path results in a        rotational position of the insertion device at the target site        being equal to the desired target rotational position based on        the representation of the inner path and the desired target        rotational position by an entry rotational position        determination unit.

In a further aspect of the present invention a rotational positioningassistance method for assisting in positioning an insertion device forbeing inserted into an object at an entry site and for being navigatedalong an inner path within the object to a target site within the objectis presented, wherein the rotational positioning assistance methodcomprises indicating a desired entry rotational position at the entrysite, which is determined by the rotational position determinationmethod, by an indication unit.

In a further aspect of the present invention a rotational positioningmethod for positioning an insertion device for being inserted into anobject at an entry site and for being navigated along an inner pathwithin the object to a target site within the object is presented,wherein the rotational positioning method comprises positioning theinsertion device at the entry site in an entry rotational position,which is determined by the rotational position determination method, bythe rotational positioning apparatus.

In a further aspect of the present invention a computer program fordetermining a rotational position of an insertion device for beinginserted into an object at an entry site and for being navigated alongan inner path within the object to a target site within the object ispresented, wherein the computer program comprises program code means forcausing the rotational position determination apparatus to carry out thesteps of the rotational position determination method, when the computerprogram is run on a computer controlling the rotational positiondetermination apparatus.

It shall be understood that the rotational position determinationapparatus, the rotational positioning assistance apparatus, therotational positioning apparatus, the rotational position determinationmethod, the rotational positioning assistance method, the rotationalpositioning method and the computer.

These and other aspects of the invention will be apparent from andelucidated with reference to the embodiments described hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following drawings:

FIG. 1 shows schematically and exemplarily an embodiment of a rotationalposition determination apparatus, an embodiment of a rotationalpositioning assistance apparatus and an embodiment of a rotationalpositioning apparatus being used in an interventional procedure;

FIG. 2 shows schematically and exemplarily an embodiment of an insertiondevice;

FIG. 3 shows schematically and exemplarily another embodiment of aninsertion device;

FIG. 4 shows schematically and exemplarily an introducer sheath forproviding an access to a femoral artery;

FIG. 5 shows schematically and exemplarily an arrangement for rotating adelivery unit relative to the introducer sheath; and

FIG. 6 shows a flowchart exemplarily illustrating an embodiment of arotational position determination method for determining an entryrotational position.

DETAILED DESCRIPTION OF EMBODIMENTS

FIG. 1 shows schematically and exemplarily an embodiment of a rotationalposition determination apparatus 15, an embodiment of a rotationalpositioning assistance apparatus 16 and an embodiment of a rotationalpositioning apparatus 20, which are used in an interventional procedure,in which an insertion device is inserted into a person 2 at an entrysite 5 and navigated along an inner path 8 within the person 2 to atarget site 6.

The rotational position determination apparatus 15 is adapted todetermine an entry rotational position defining the rotational positionof the insertion device at the entry site 5. The rotational positiondetermination apparatus 15 comprises a three-dimensional vessel geometrymodel providing unit 9 for providing a three-dimensional vessel geometrymodel representing a vascular network of the person 2. Preferentially,the three dimensional vessel geometry model providing unit 9 is adaptedto generate a three-dimensional image of a vascular network of theperson 2 and to segment the three-dimensional image for extracting thethree-dimensional vessel geometry model. The three-dimensional image is,for example, a computed tomography image, a magnetic resonance image oran image generated by another imaging modality. The three-dimensionalvessel geometry model providing unit 9 can also be a storing unit, inwhich the three-dimensional vessel geometry model is stored already andfrom which the stored three-dimensional vessel geometry model can beprovided.

The rotational position determination apparatus 15 further comprises aninner path providing unit 3 for providing a representation of the innerpath 8 within the person 2. In this embodiment, the inner path providingunit 3 is adapted to determine the inner path 8 by determining a paththrough the provided three-dimensional vessel geometry model from theentry site 5 to the target site 6. The inner path providing unit 3 can,for example, be adapted to determine the shortest path within the person2, which has a diameter being sufficiently large for moving theinsertion device from the entry site 5 to the target site 6. In anotherembodiment, also the inner path providing unit 3 can be a storing unit,in which the inner path is stored already and from which the inner pathcan be provided. The inner path providing unit can also be a receivingunit for receiving the inner path via a wired or wireless dataconnection, wherein the inner path providing unit is adapted to providethe received inner path. Also the three-dimensional vessel geometrymodel providing unit can be a receiving unit for receiving thethree-dimensional vessel geometry model and for providing the receivedthree-dimensional vessel geometry model.

The rotational position determination apparatus 1 further comprises aninner path length determination unit 12 for determining the length ofthe inner path 8 based on the provided representation of the inner path8. Since the inner path 8 is known in the three-dimensional vesselgeometry model, the inner path 8 can be determined by calculating thelength of the inner path 8 within the three dimensional vessel geometrymodel.

The rotational position determination apparatus 15 further comprises aninner path element selection unit being, in this embodiment, a deliverysystem selection unit 13 for selecting a delivery system for deliveringthe insertion device to the target site 6, wherein the delivery systemselection unit 13 is adapted to select the delivery system depending onthe determined length of the inner path. In this embodiment, thedelivery system comprises a guidewire and a delivery unit, wherein thedelivery unit is adapted to hold the insertion device and to be movedalong the guidewire, in order to deliver the insertion device from theentry site 5 to the target site 6. In FIG. 1, the delivery system isrepresented by the guidewire 14. The delivery system selection unit 13can, for example, be adapted to select one or several guidewires havinga length which fits to the length of the inner path. For instance, thedelivery system selection unit 13 can comprise a data base, in which anassignment between delivery systems and possible lengths of the innerpath are stored, wherein a suitable delivery system can be selected fromthe data base based on the assignments. The delivery system selectionunit 13 can also be adapted to select a delivery system based on othercharacteristics of the inner path like the minimal diameter along theinner path, the location of the inner path, et cetera. The deliverysystem selection unit 13 is preferentially adapted to not only selectthe length of the respective guidewire as part of a delivery system, butto also select a delivery unit for delivering the insertion device alongthe guidewire within the person. The delivery system selection unit canfurther be adapted to select other endovascular devices, which may beused during the interventional procedure, based on characteristics ofthe provided representation of the inner path 8.

The rotational position determination apparatus 15 further comprises atarget rotational position providing unit 4 for providing a desiredtarget rotational position of the insertion device at the target site 6.In this embodiment, the insertion device is a fenestrated stent 10 witha window 39 as schematically and exemplarily shown in FIG. 2. The window39 is provided for allowing the fenestrated stent 10 to be introducedinto a branched vessel without closing a branch of the vessel. Inanother embodiment, the insertion device can also be a two-legged stent11 as schematically and exemplarily shown in FIG. 3.

The target rotational position providing unit 4 is adapted to determinethe target rotational position such that the endovascular device 10 fitsto the vessel configuration at the target site 6. In this embodiment, abranch 30 is present at the target site 6. The target rotationalposition providing unit 4 is adapted to determine the target rotationalposition of the fenestrated stent shown in FIG. 2 such that the window39 of the stent 10 is aligned with the opening 31 of the main vessel 32to the branch vessel 33. The target rotational position providing unit 4determines a rotational position of a landmark of the insertion device,wherein the landmark is, for example, the window 39 or another marker onthe stent. If the delivery unit delivers the insertion device 10 to thetarget site 6, for example, along a guidewire 14, wherein there is afixed and known spatial relationship between the insertion device 10 andthe delivery unit, also a marker on the delivery unit can be used as alandmark, wherein the rotational position of this landmark can beprovided by the target rotation position providing unit 4 for indicatingthe target rotational position.

In another embodiment, also the target rotational position providingunit can be a storage unit, in which the desired target rotationalposition of the insertion device at the target site is stored already,wherein the stored desired target rotational position can be retrievedfrom the storage unit 4 for providing the desired target rotationalposition. Moreover, the target rotational position providing unit canalso be a receiving unit for receiving the target rotational positionvia a wired or wireless data connection, wherein the desired targetrotational position can have been determined automatically orsemi-automatically by another unit, or the target rotational positioncan be input by a user.

The rotation position determination apparatus 15 further comprises anentry rotational position determination unit 7 for determining the entryrotational position such that a navigation of the insertion device 10from the entry site 5 to the target site 6 along the inner path 8results in a rotational position of the insertion device 10 at thetarget site 6 being equal to the target rotational position based on therepresentation of the inner path and the desired target rotationalposition. The entry rotational position determination unit 7 can beadapted to simulate the navigation of the insertion device 10 from theentry site 5 to the target site 6 based on the representation of theinner path and the target rotational position for determining the entryrotational position. In particular, the entry rotational positiondetermination unit 7 can be adapted to simulate the trajectory of thedelivery unit, which is used for delivering the insertion device 10 fromthe entry site 5 to the target site 6 through the representation of theinner path, in particular, through the three-dimensional vessel geometrymodel along the inner path, while keeping track of the orientation ofthe landmark. The entry rotational position determination unit 7 can beadapted to use a known simulation method like the simulation methodsdisclosed in, for example, the article “Simulation of guidewirenavigation in complex vascular structures” by V. Guilloux et al.,Medical Imaging 2006: Visualization, Image-Guided Procedures, andDisplay, 6141: 14107-14107 (2006), the article “Remote manipulation ofguidewire using an virtual reality device” by K. Fukasaku et al.,Interventional Neuroradiology, 7: 29-34 Suppl. (1 Dec. 2001); and thearticle “A real-time interactive surgical simulator for catheternavigation” by Lim et al., Surgical-Assist Systems, Proceedings of SPIE,3262: 4-14 (1998), which are herewith incorporated by reference. Anotherknown simulation method, which could be used by the entry rotationalposition determination unit, is disclosed in the article “Development ofa training system for interventional radiology” by M. Ide et al.,Modelling in Medicine and Biology VIII, 313-322 (2009), which is alsoincorporated by reference.

In an embodiment, the entry rotational position determination unit 7 canalso be adapted to determine the entry rotational position withoutperforming a simulation. For example, if, in an embodiment, the innerpath is relatively straight and has a relatively large diameter suchthat a rotation of the insertion device 10 is not required while beingnavigated from the entry site 5 to the target site 6, the entryrotational position can be determined as being equal to the targetrotational position, or, if it is known from, for instance, a database,that a navigation along the actual inner path requires a rotation of theinsertion device 10 by a certain known angle, the entry rotationalposition can be determined based on the provided target rotationalposition and the certain known angle, without necessarily performing asimulation.

The rotational positioning assistance apparatus 16 is adapted to assistin positioning the insertion device 10 at the entry site 5. Therotational positioning assistance apparatus 16 comprises an actual entryrotation position determination unit 17 for determining an actual entryrotational position of the insertion device 10 at the entry site 5. Inthis embodiment, the actual entry rotational position determination unit17 is adapted to determine the actual entry rotational position of theinsertion device 10 at the entry site 5 based on a fluoroscopy imagegenerated by a fluoroscopy apparatus 34. The fluoroscopy apparatus 34comprises a radiation source 22, in particular, an x-ray source, and adetection unit 23 for detecting the radiation 35 emitted by theradiation source 22 after having traversed the person 2. The fluoroscopyapparatus 34 further comprises a fluoroscopy control unit 24 forcontrolling the radiation source 22 and the detection unit 23 and forproviding the fluoroscopy image to, for example, the rotationalpositioning assistance apparatus 16. The fluoroscopy apparatus 34 is,for example, a C-arm apparatus.

The landmark on the insertion device 10 is chosen such it is detectablein the fluoroscopy image. In particular, the landmark can be the window39, which is detectable in the fluoroscopy image, or another mark on theinsertion device 10 or on the delivery unit. The actual entry rotationalposition can therefore be determined by detecting the landmark in thefluoroscopy image.

The rotational position determination apparatus 15 further comprises anentry path providing unit 48 for providing an entry path from theoutside of the person 2 to an end of the inner path 8 at the entry site,wherein the entry rotational position determination unit 7 can beadapted to determine the entry rotational position such that thenavigation of the insertion device 10 from the entry site 5 to thetarget site 6 along the entry path and the inner path 8 results in arotational position of the insertion device at the target site beingequal to the target rotational position based on the representation ofthe entry path, the representation of the inner path and the desiredtarget rotational position. A possible arrangement at the entry site 5is schematically and exemplarily shown in more detail in FIG. 4.

FIG. 4 shows schematically and exemplarily an introducer sheath 41,which has been introduced into a femoral artery 40 through tissue 43, inorder to provide an access of the insertion device 10 to the femoralartery 40. The introducer sheath 41 is visible in the fluoroscopy imagesuch that the entry path providing unit 48 can detect the introducersheath 41 and determine the entry path 42 from the detected introducersheath 41 for providing the entry path 42. For example, the introducersheath 41 can comprise markers, which are visible in the fluoroscopyimage, in order to determine the entry path based on the fluoroscopyimage.

The entry rotational position determination unit 7 can be adapted tofirstly determine an intermediate entry rotational position at the end49 of the inner path 8 such that a navigation of the insertion device 10from the end 49 to the target site 6 along the inner path 8 results in arotational position of the insertion device 10 at the target site 6being equal to the desired target rotational position based on therepresentation of the inner path 8 and the provided desired targetrotational position. The resulting intermediate rotational position 44is schematically and exemplarily indicated at the end 49 of the innerpath 8 with respect to a reference rotational position 45 in a planebeing perpendicular to a tangent of the centre line 50 of the femoralartery 40.

The entry rotational position determination unit 7 can be furtheradapted to determine the entry rotational position at the outside 51based on the intermediate entry rotational position 44 and the providedrepresentation of the entry path 42. The resulting final entryrotational position 46 can be determined in a plane being substantiallyperpendicular to the centre line of the introducer sheath at the entrysite 5 and can be calculated with respect to an external referencerotational position 47, which has a known relation with a correspondinginternal reference rotational position 45. In particular, the finalentry rotational position 46 is preferentially defined in a normal planebeing perpendicular to the tangent vector of the centre line of theintroducer sheath at the outside 51. If desired, the final entryrotational position can be projected on any other plane, which may notbe perpendicular to the tangent vector, except for planes which containthe tangent vector. For example, the final entry rotational position canbe projected onto a plane defined by the ring-shaped elements shown inFIG. 5.

If in an embodiment the planes at the end 49 of the inner path 8 and atthe outside 51 are both equally oriented with respect to the tangent tothe centre line of the introducer sheath 41, for example, perpendicularto the tangent, the reference rotational positions in these planes canbe provided such that they describe how a rotational position of theinsertion device will be modified, while being moved from the outsidelocation 51 to the inside location 49. Thus, if in this embodiment anintermediate entry rotational position has been determined enclosing anangle α with a reference rotational position at the end 49 of the innerpath 8 in a plane having a certain orientation with respect to thetangent to the centre line of the introducer sheath 41, the desiredentry rotational position at the outside location 51 can be determinedby adding the same angle α to the reference rotational position in aplane having the same certain orientation to the tangent at the outsidelocation 51. The desired entry rotational position at the outsidelocation 51 can be provided in another plane having another orientationby projecting the desired rotational position, which has been determinedfor the plane having the certain orientation with respect to the tangentat the outside location 51, onto the other plane having the otherorientation. Moreover, also the intermediate entry rotational positionat the end 49 of the inner path 8 can firstly be provided in a planehaving an orientation being different to the certain orientation withrespect to the tangent at the end 49 of the inner path 8, wherein theintermediate entry rotational position can be projected onto the planehaving the certain orientation with respect to the tangent to the centreline of the introducer sheath 41. In general the intermediate entryrotational position at the end 49 of the inner path 8 and the desiredentry rotational position at the outside 51 can be provided indifferently oriented planes.

The rotational positioning assistance apparatus 16 further comprises adeviation calculation 18 for calculating a deviation between the actualentry rotational position and the desired entry rotational positiondetermined by the entry rotational position determination unit 7 and anindication unit 19 for indicating a desired entry rotational position atthe entry site 5 determined by the entry rotational positiondetermination unit 7. In particular, the indication unit 19 is a displayshowing the entry rotational position. In this embodiment, theindication unit 19 is adapted to indicate the desired entry rotationalposition by indicating the deviation calculated by the deviationcalculation unit 18. The indication unit 19 can show a text advising theuser to rotate the insertion device by a certain rotational angle in acertain rotational direction as defined by the calculated deviation. Inaddition or alternatively, the indication unit 19 can show a graphicaltool representing the calculated deviation like a cartoon with thecorrect orientation of the insertion device 10 relative to the actualentry rotational position or an arrow. The deviation can also be shownas a graphical overlay on top of the fluoroscopy image, for example,similar in principle to the overlay image provided by thethree-dimensional image needle guidance system XperGuide of the companyPhilips.

The rotational positioning apparatus 20 is adapted to position theinsertion device 10 at the entry site 5. The rotational positioningapparatus 20 is not shown in FIG. 4 for clarity reasons, i.e. in orderto clearly show the relation between the rotational positions at theends of the entry path. However, an embodiment of the rotationalpositioning apparatus 20 is exemplarily and schematically shown in moredetail in FIG. 5.

The rotational positioning apparatus 20 comprises two ring-shapedelements 52, 53, which are movable with respect to each other. A firstring-shaped element 52 can be fixed to the person 2 by using a fixationsystem like a belt, glue, et cetera. Moreover, the first ring-shapedelement 52 is fixed with respect to the introducer sheath 41. A secondring-shaped element 53 encloses a delivery unit 54 or, if a deliveryunit is not used, the insertion device, wherein the delivery unit 54 cantemporarily be fixed to the second ring-shaped element 53, in order torotate the delivery unit 54 with respect to the introducer sheath 41 bymoving the second ring-shaped element 53 with respect to the firstring-shaped element 52. The rotational positioning apparatus 20 can beadapted to allow a user to manually rotate the second ring-shapedelement 53 with respect to the first ring-shaped element 52 and/or therotational positioning apparatus 20 can be adapted to rotate the secondring-shaped element 53 with respect to the first ring-shaped element 52by using one or several motors included in at least one of the first andsecond ring-shaped elements 52, 53. The delivery unit 54 or, if theinsertion device is inserted without using the delivery unit 54, theinsertion device 10 can be temporarily fixed to the second ring-shapedelement 53 by using fixation elements like screws, which can be movedradially, in order to hold the delivery unit 54 at a fixed position withrespect to the second ring-shaped element 53. Alternatively or inaddition, at least around the opening of the ring-shaped element 53 thesecond ring-shaped element 53 can be made of an elastic material like,for example latex, in order to temporally hold the delivery unit 54 at afixed position with respect to the second ring-shaped element 53. Theindication unit 19 can indicate the correct desired entry rotationalposition such that a user can rotate the delivery unit 54 to the correctdesired entry rotational position by rotating the second ring-shapedelement 53 with respect to the first ring-shaped element 52.Alternatively or in addition, indications for indicating the correctdesired entry rotational position can also be provided on the rotationalpositioning apparatus 20. For example, indications 55 and 56 can beprovided on the first and second ring-shaped elements 52, 53,respectively, wherein at least one of these indications 55, 56 can bemovable with respect to the respective first or second ring-shapedelement 52, 53, in order to allow the rotational positioning apparatus20 to indicate the correct desired entry rotational position. Forexample, one of these indications 55, 56 can be provided bylight-emitting diodes distributed over the circumference of therespective ring-shaped element.

The delivery unit 54 can comprise an indication 57, wherein a user canalign the indications 57 and 56, in order to arrange the delivery unit54 within the upper ring-shape element 53 in a known rotational positionwith respect to the upper ring-shaped element 53. Thus, in an embodimentthe rotational position determination apparatus can be adapted todetermine the positions and orientations of the different elements,except for the delivery unit 54, with respect to a reference system byusing, for example, a fluoroscopy image showing the introducer sheath 41and the ring-shaped elements 52, 53 and by registering the fluoroscopyimage with a pre-operatively acquired image, which has been used fordetermining the inner path. The rotational position of the delivery unit54 with respect to the reference system can then be determined byarranging the delivery unit 54 within the ring-shaped element 53 suchthat the indications 57 and 56 are aligned. However, in anotherembodiment the fluoroscopy image can also show the delivery unit 54 suchthat the rotational position of the delivery unit 54 can be determinedwith respect to the reference system, without aligning the indications56 and 57.

The rotational positioning apparatus 20 can be connected to therotational positioning assistance apparatus 16, in order to allow therotational positioning apparatus 20 to rotate the insertion device 10 tothe correct rotational position based on the calculated deviation. Inanother embodiment, the rotational positioning apparatus can haveanother construction for rotating the insertion device, in particular,for rotating a delivery unit comprising the insertion device, forpositioning the insertion device in the correct entry rotationalposition at the entry site.

After the insertion device 10 has been rotated to the correct entryrotational position, the insertion device 10 is navigated to the targetsite 6, for example, by using a delivery system. Since the insertiondevice has been arranged at the correct entry rotational position, theinsertion device 10 is also correctly oriented at the target site 6. Inparticular, at the target site 6 the window 39 of the stent 10 isaligned with the opening 31 from the main vessel 32 to the branch vessel33.

FIG. 6 shows a flowchart exemplarily illustrating an embodiment of arotational position determination method for determining a rotationalposition of an insertion device for being inserted into an object at anentry site and for being navigated along an inner path within the objectto a target site within the object.

In step 101, the representation of the inner path within the object isprovided by the inner path providing unit 3. The inner path can beprovided by, for example, providing a three-dimensional vessel geometrymodel representing a vascular network of the object and by determining apath through the three-dimensional vessel geometry model from the entrysite to the target site. In step 102, a desired target rotationalposition of the insertion device at the target site is provided by thetarget rotational position providing unit 4. In particular, the targetrotational position providing unit 4 determines the target rotationalposition such that the insertion device fits to the vessel configurationat the target site. In step 103, the entry rotational position isdetermined such that a simulation of the navigation of the insertiondevice from the entry site to the target site along the representationof the inner path results in a rotational position of the insertiondevice at the target site being equal to the target rotational positionby the entry rotational position determination unit 7.

In step 104, the determined entry rotational position at the entry siteis indicated by the indication unit 19. In particular, the actual entryrotational position determination unit 17 can determine the actual entryrotational position of the insertion device at the entry site, thedeviation calculation unit 18 can calculate a deviation between theactual rotational position and the determined desired entry rotationalposition, wherein the indication unit 19 can indicate the entryrotational position by indicating the deviation. In step 104,alternatively or in addition, the insertion device can be positioned atthe entry site in the correct entry rotational position by using therotational positioning apparatus 20.

In step 103, an entry rotational position can be determined at theoutside of the person 2 at the entry site by considering therepresentation of the inner path and a representation of an entry pathas described above. Moreover, in step 103 instead of using a simulationthe entry rotational position can be determined in another way, forexample, by using a data base providing changes of the rotationalposition obtained while navigating the insertion device along the innerpath and optionally along the entry path depending on characteristics ofthe inner path and optionally the entry path determined from therespective representations.

The above described apparatus is a method which may be adapted to beused for the treatment of abdominal aortic aneurism (AAA) and ofthoracoabdominal aortic aneurism (TAAA), wherein fenestrated(two)-legged stents or multi-branched stents may be implanted. Thecorrect positioning of such stents in relation to the patient-specificaortic anatomy is of extreme importance. In the case of a fenestratedstent, the apertures of the stent have to be correctly aligned with thecorresponding aortic side branches and no important side branch shouldbe covered. In the case of branched stents, the branches of the stenthave to correctly match the aortic branches.

The rotational position determination apparatus, the rotationalpositioning assistance apparatus and/or the rotational positioningapparatus are preferentially adapted to be used for performing astenting procedure involving inserting a guidewire, for example, throughthe femoral artery, which serves as a monorail to guide the insertiondevice, in particular, a stent delivery unit with the insertion device,and optionally any other needed devices such as angioplasty balloons,from the entry site to the target site.

Most available delivery units used to deploy such stents have limited orno possibility of being rotated after they arrive at their deploymentposition which implies that they should be inserted with the (near)correct angle so that, when deployed, landmarks (for example, apertures,in the case of fenestrated stents, or branches, in the case of branchedstents) will be aligned with the appropriate vessels. If this is notachieved in the first try, it may be necessary to retrieve, rotate andreinsert the delivery unit until the desired alignment is obtained.

Since the above described rotational position determination apparatusand method determines a correct entry rotational position of theinsertion device, the need of re-insertions due to wrong alignment canbe reduced. Ideally, a re-insertion is not needed at all, because, ifthe insertion device is arranged at the correct rotational position atthe entry site, the insertion device is also in the correct rotationalposition at the target site. In order to determine the correctrotational position at the target site, the rotational positiondetermination apparatus and method can be adapted to keep track of theangular orientation of the insertion device, in particular, of thedelivery unit comprising the insertion device, during a simulation ofthe trajectory through the segmented model of the vascular network ofthe person. The rotational position determination apparatus and methodcan be adapted to be used independently of a delivery system choice.

The rotational position determination apparatus and method can beadapted to determine the entry rotational position pre-operatively orjust before an intervention.

The rotational position determination apparatus and method can beadapted to be used in interventional x-ray. The rotational positiondetermination method can be implemented in software, wherein thesoftware can be implemented in, for example, XtraVision platform of thecompany Philips, or as a stand-alone application targeted for stent(-graft) planning. The rotational position determination apparatus 15,the rotational positioning assistance apparatus 16 and the rotationalpositioning apparatus 20 can each be regarded as being an independentdevice, which can be an accessory for interventional x-ray systems.

The rotational position determination apparatus, the rotationalpositioning assistance apparatus and the rotational positioningapparatus can be regarded as being separate apparatuses, or they can beregarded as being comprised by a single apparatus. For example, therotational position determination apparatus can comprise the rotationalpositioning assistance apparatus and/or the rotational positioningapparatus.

The above-mentioned introducer sheath is preferentially rigid, i.e.maintains its form, and has preferentially special marks in the partthat will be introduced into the person at the entry site, inparticular, that will be introduced into the femoral artery. The specialmarks are positioned in such a way that it is possible to register theangular positioning of the introducer sheath with respect to thethree-dimensional image obtained pre-operatively for determining therepresentation of the inner path. The finally determined desired entryrotational position may be indicated on the exterior of the introducersheath, i.e. the exterior of the introducer sheath may comprise theindication unit.

In another embodiment, after the introducer sheath has been introduced,the three-dimensional image obtained pre-operatively can be registeredwith the fluoroscopy image, wherein the markers of the introducer sheathcan be used to register the angular positioning of the introducer sheathwith respect to the three-dimensional image obtained pre-operatively.The registration result yields the entire path from the outside of theperson at the entry site to the target site including the entry path andthe inner path, thereby allowing to determine the correct entryrotational position at the outside of the person at the entry site, inparticular, with respect to an introducer exterior plane.

In a further embodiment, a specially marked catheter can be used, whichcan be adapted to be inserted into the femoral artery in order toachieve the alignment, i.e. in order to arrange the insertion device atthe entry site in the correct rotational entry position. The desiredentry rotational position could, for example, be marked on an introducersheath, through which the catheter may be inserted into the person, oron a leg of the person in case no introducer sheath is used or in anexternal apparatus that can be attached to an existing introducersheath.

In a further embodiment, after the introducer sheath has beenintroduced, a three-dimensional image of the entry site can be generatedby using, for example, rotational x-ray. The three-dimensional image canbe aligned with and registered to the image of the vascular three usedfor determining the representation of the inner path. After thisregistration has been performed, the entire path including the innerpath and the entry path are defined such that the entry rotationalposition at the outside of the person at the entry site, in particular,with respect to an introducer plane at the outside of the person, can bedetermined, for example, by simulating the trajectory of the insertiondevice or of a delivery unit holding the insertion device from theintroducer entry, i.e. from the outside of the person at the entry site,to the target site. In particular, firstly an intermediate entryrotational position can be determined at the end of the inner path atthe entry site and then the final entry rotational position at theoutside of the person at the entry site can be determined based on therepresentation of the entry path and the intermediate entry rotationalposition. Alternatively, instead of a three-dimensional image of theintroducer site two orthogonal images can be acquired and used for thealigning and registration procedure.

Although in an above described embodiment an indication unit 19 forindicating an entry rotational position at the entry site is part of therotational positioning assistance apparatus 16, in other embodiments theindication unit can also be a separate unit or can be a part of anotherunit or apparatus. For example, the rotational positioning apparatus 20,in particular, the introducer, can comprise a display for indicating thecorrect entry orientation of the insertion device or of the deliveryunit, if the insertion device is held by the delivery unit, at the entrysite by means of, for instance, a rotating arrow, light, et cetera. Asalready mentioned above, the indication unit can also be a separateunit, which can be attached to an existing introducer sheath, whereinthe indication unit can comprise a display for indicating the correctentry rotation position of the insertion device and/or of the deliveryunit by means of, for instance, a rotating arrow, light, et cetera.

Other variations to the disclosed embodiments can be understood andeffected by those skilled in the art in practicing the claimedinvention, from a study of the drawings, the disclosure, and theappended claims.

In the claims, the word “comprising” does not exclude other elements orsteps, and the indefinite article “a” or “an” does not exclude aplurality.

A single unit or device may fulfill the functions of several itemsrecited in the claims. The mere fact that certain measures are recitedin mutually different dependent claims does not indicate that acombination of these measures cannot be used to advantage.

Determinations like the determination of an inner path, thedetermination of a target rotational position, the determination of anentry rotational position et cetera performed by one or several units ordevices can be performed by any other number of units or devices. Thedeterminations and/or the control of the rotational positiondetermination apparatus in accordance with the rotational positiondetermination method and/or the control of the rotational positioningassistance apparatus in accordance with the rotational positioningassistance method and/or the control of the rotational positioningapparatus in accordance with the rotational position determinationmethod can be implemented as program code means of a computer programand/or as dedicated hardware.

A computer program may be stored/distributed on a suitable medium, suchas an optical storage medium or a solid-state medium, supplied togetherwith or as part of other hardware, but may also be distributed in otherforms, such as via the Internet or other wired or wirelesstelecommunication systems.

Any reference signs in the claims should not be construed as limitingthe scope.

The invention relates to a rotational position determination apparatusfor determining an entry rotational position, which defines a rotationalposition of an insertion device like a stent at an entry site, such thata navigation of the insertion device from the entry site to a targetsite along an inner path results in a rotational position of theinsertion device at the target site being equal to a desired targetrotational position based on a representation of the inner path and thedesired target rotational position. If the insertion device is arrangedin the determined entry rotational position at the entry site and thennavigated to the target site, it is therefore not necessary to rotatethe insertion device at the target site, i.e. it is not necessary to usea technically complex interventional device for rotating the insertiondevice at the target site.

1. A rotational positioning assistance apparatus for assisting in positioning an insertion device for being inserted into an object at an entry site and for being navigated along an inner path within the inner object to a target site within the object, wherein the rotational positioning assistance apparatus comprises an indication unit (19) for indicating a desired entry rotational position at the entry site determined by a rotational position determination apparatus, said rotational position determination apparatus configured to determine a rotational position of an insertion device for being inserted into an object and for being navigagted along an inner path wirthin the object from an entry site to a target site within the object, the rotational position determination apparatus comprising a computer and a memory with instructions that, when executed by the computer, configure the computer to: provide a representation of the inner path within the object, provide a desired target rotational position of the insertion device at the target site, determine an entry rotational position, which defines a rotational position of the insertion device at the entry site, such that a navigation of the insertion device from the entry site to the target site along the inner path results in a rotational position of the insertion device at the target site being equal to the desired target rotational position based on the representation of the inner path and the desired target rotational position, and provide an output for indicating the determined entry rotational position.
 2. A rotational positioning apparatus for positioning an insertion device (10) for being inserted into an object (2) at an entry site and for being navigated along an inner path within the inner object to a target site within the object, wherein the rotational positioning apparatus (20) comprises a positioning unit (27, 28, 29) for positioning the insertion device (10) at the entry site (5) in an entry rotational position determined by a rotational position determination apparatus, the rotational position determination apparatus comprising a computer and a memory with instructions that, when executed by the computer, configure the computer to: provide a representation of the inner path within the object; provide a desired target rotational position of the insertion device at the target site; determine an entry rotational position, which defines a rotational position of the insertion device at the entry site, such that a navigation of the insertion device from the entry site to the target site along the inner path results in a rotational position of the insertion device at the target site being equal to the desired target rotational position based on the representation of the inner path and the desired target rotational position; and provide an output for indicating the determined entry rotational position.
 3. A rotational positioning assistance method for assisting in positioning an insertion device for being inserted into an object at an entry site and for being navigated along an inner path within the object to a target site within the object, wherein the rotational positioning assistance method comprises indicating a desired entry rotational position at the entry site, which is determined by a rotational position determination method, the rotational position determination method comprising act of: providing a representation of the inner path within the object by a computer; providing a desired target rotational position of the insertion device at the target site by the computer; determining an entry rotational position, which defines a rotational position of the insertion device at the entry site, such that a navigation of the insertion device from the entry site to the target site along the inner path results in a rotational position of the insertion device at the target site being equal to the desired target rotational position based on the representation of the inner path and the desired target rotational position by the computer; and providing by the computer an output for indicating the determined entry rotational position by an indication unit (19).
 4. A rotational positioning method for positioning an insertion device for being inserted into an object at an entry site and for being navigated along an inner path within the object to a target site within the object, wherein the rotational positioning method comprises positioning the insertion device at the entry site in an entry rotational position, which is determined by a rotational position determination method comprising acts of: providing a representation of the inner path within the object by a computer; providing a desired target rotational position of the insertion device at the target site by the computer; determining an entry rotational position, which defines a rotational position of the insertion device at the entry site, such that a navigation of the insertion device from the entry site to the target site along the inner path results in a rotational position of the insertion device at the target site being equal to the desired target rotational position based on the representation of the inner path and the desired target rotational position by the computer; and providing by the computer an output for indicating the determined entry rotational position, by a rotational positioning apparatus as defined in claim
 2. 5. A system characterized in that the system comprises: a rotational position determination apparatus for determining a rotational position of an insertion device for being inserted into an object and for being navigated along an inner path within the object from an entry site to a target within the object, the rotational position determination apparatus comprising a computer and a memory with instructions that, when executed by the computer, configure the computer to: provide a representation of the inner path within the object, provide a desired target rotational position of the insertion device at the target site, determine an entry rotational position, which defines a rotational position of the insertion device at the entry site, such that a navigation of the insertion device from the entry site to the target site along the inner path results in a rotational position of the insertion device at the target site being equal to the desired target rotational position based on the representation of the inner path and the desired target rotational position, and provide an output for indicating the determined entry rotational position; a rotational positioning assistance apparatus for assisting in positioning the insertion device at the entry site; and a rotational positioning apparatus for positioning the insertion device at the entry site. 